Lee Frelich's "Climate Change & Forests" Presentation

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Within the next 50–100 years, the warming climate will have major effects on boreal and northern hardwood forests situated near the prairie–forest border of central North America.

This biome boundary shifted to the northeast
during past episodes of global warming, and is expected to do so again. The climate of the future will likely lead to higher mortality among mature trees, due to the greater frequency of droughts, fires, forest-leveling windstorms, and outbreaks of native and exotic insect pests and diseases. In addition, increasing populations of native deer and European earthworm invasions will inhibit the establishment of tree seedlings. The expected net impact of these factors will be a “savannification” of the forest, due to loss of adult trees at a rate faster than that at which
they can be replaced. This will cause a greater magnitude and more rapid northeastward shift of the prairie–forest
border, as compared with a shift solely attributable to the direct effects of temperature change.

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Lee Frelich's "Climate Change & Forests" Presentation

  1. 1. Dave Hansen Univ. of MN Climate change, invasive species and forests Lee E. Frelich Director, The University of Minnesota Center for Hardwood Ecology Vice President, Eastern Native Tree Society Chair, Board of Directors, Great River Greening John Knuerr
  2. 2. Svante August Arrhenius (Nobel prize, Chemistry,1903) Developed the hothouse theory for CO2 in 1896, and in 1905 predicted that raising CO2 content of the atmosphere would cause an increase in mean global temperature similar in magnitude to modern predictions
  3. 3. Evidence that CO2 increase and climate change are caused by humans 1. Keeling curve corresponds to population and known emissions of CO2 2. Suess effect 3. Temperature profile of the atmosphere—warmer lower atmosphere and cooler stratosphere 4. Existing ‘Greenhouse effect’ of 56 degree F before human enhancement of heat trapping gases in the atmosphere 5. Models with human greenhouse gas enhancement match observed temperatures over the last 100 years, models with only natural forcings on climate do not
  4. 4. Climate change occurs in the context of large year to year variability—summer temperatures for 2009
  5. 5. …and spatial variability Summer 2009—Example of regional temperature anomalies versus global mean in a warming climate. A cold summer in central and eastern North America, although 80% of the world had above average temperatures.
  6. 6. Tree ring analyses showing climate over the several hundred years Comparison of the original Mann ‘hockey stick’ reconstruction of temperature (red) with implementation of valid criticisms of the PC methodology (green). From Wahl and Amman 2006. http://www.cgd.ucar.edu/ccr/ammann/millennium/CODES_MBH.html
  7. 7. Tree ring analyses from 14 sites Osborne and Briffa 2006, instrumental record for northern hemisphere (red) and for records closest to proxy sites (green).
  8. 8. Oerlemans, 2005 temperature reconstruction of global mean temperature based on 169 glaciers.
  9. 9. Temperature evidence from boreholes Borehole temperature data from Huang, Pollock and Shen, Nature, 2000
  10. 10. Modeling of temperature showing how natural and human influences work together. From McCarthy, 2009, Science
  11. 11. Natural versus human CO2 forcing on the climate
  12. 12. British Meteorological Office, December 2009
  13. 13. Spruce White pine Migration maps for tree response to past climate change in 1000s years before present (M.B. Davis 1983)
  14. 14. Current and simulated future range of black spruce, from Lenihan and Neilson 1995. 300 mile shift is equal to distance moved in ~ 2000 years in paleorecord
  15. 15. Forest cover of central North America (green) DeFries, R., M. Hansen, J.R.G. Townshend, A.C. Janetos, and T.R. Loveland (2000), 1 Kilometer Tree Cover Continuous Fields, 1.0, Department of Geography, University of Maryland, College Park, Maryland, 1992-1993. It is possible that the pbf will move 500 km to the north and east, deforesting an area 2X the size of California
  16. 16. Native species have migrated in the past without going extinct what’s different now? Rate of climate change—many species cannot migrate fast enough Fragmented environment—makes species to movement more difficult Habitat loss—less habitat now and can support fewer species Invasive species—can reproduce and move fast, they have opportunity to displace native species during times of rapid change Exotic diseases and pests—can spread faster in a warmer climate Deer grazing—will increase in the north, can extirpate native plants TNC David Augustine
  17. 17. Minneapolis Star tribune Before and after the 1999 blowdown in the Boundary Waters, northern MN
  18. 18. Wind plus fire = major forest transformation Nick Fisichelli and Roy Rich, Cavity Lake Burn, Seagull Lake, July 2007. Photo: Dave Hansen, University of MN
  19. 19. Several forces are at work that may push MN forests towards savanna: If soils become drier for any reason sites can support fewer trees: Warmer soils Higher evaporation to precipitation ratio European earthworms stripping the insulating duff layer
  20. 20. Photo: Dave Hansen More drought = trees under stress and forest dieback
  21. 21. Native insects play a major role in forest change Benign native insects can have outbreaks in a warmer climate. For example, mountain pine beetle in British Columbia—a native insect that caused massive tree mortality over 30 million acres of lodgepole pine forest, and could threaten jack pine in MN
  22. 22. Sylvania Wilderness maple and hemlock forest in 1988
  23. 23. Sylvania in 2006
  24. 24. Global warming or Global worming? Earthworms are ecosystem engineers that can alter the structure of soil, and change the H2O, N and P cycles, C dynamics and seedbed characteristics on a regional scale
  25. 25. Photos: Dave Hansen, University of MN Soil profile, no earthworms (left), with earthworms (right). The loss of the duff layer will affect summer soil temperature
  26. 26. Earthworm invasion in maple forest causes a decrease in tree ring width and loss of seedling density and herb species on the forest floor 1.6 1.4 Ring width index 1.2 1 Worm free 0.8 0.6 worm invaded 0.4 0.2 0 -5 0 5 10 15 20 25 30 Invasion timing (years)
  27. 27. Recent literature shows that Earthworms also facilitate germination and establishment of European buckthorn and garlic mustard by changing the seed bed Photos: The Nature Conservancy Kathleen Knight
  28. 28. Exotic earthworms + deer = major transformation of the forest. Bare soil and lower nutrient status should favor hemlock over maple, but deer favor maple. Both dominant species are disfavored, combined with warmer climate and sandy soils, probably means Sylvania will become oak savanna in the future
  29. 29. Summary of impacts on Lake States tree species Global warming and rate of migration: All species Sudden oak death: red oak, pin oak Deer: white cedar, yellow birch, white pine, oaks Balsam woolly adelgid: balsam fir Emerald ash borer: green ash, black ash, white ash Paul Jost Asian long-horned beetle: red maple, sugar maple, aspen Hemlock woolly adelgid: hemlock Mountain pine beetle: jack pine Native insects: eastern larch, others Earthworms: sugar maple and others
  30. 30. Overall scheme for change at the prairie-forest border proposed by Frelich and Reich
  31. 31. Lee Frelich We can expect a messy transition History shows that development of a new ecosystem takes 100s to 1000 years to develop Old Dave Hansen Transitional New
  32. 32. Questions? Layne Kennedy Lee Frelich and clones at work during Ham Lake Fire, Seagull Lake, May 6, 2007

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